Booklet makers are well-known devices for forming folded booklets which are stapled along the crease thereof. It is becoming common to include booklet makers in conjunction with office-range copiers and printers (as used herein, a “copier” will be considered a type of “printer”). In basic form, a booklet maker includes a slot for accumulating signature sheets, as would be produced by a printer. The accumulated sheets, forming the pages of a booklet, are positioned within the stack so that a stapler mechanism and complementary anvil can staple the stack precisely along the intended crease line. In one embodiment, the creased and stapled sheet sets are then pushed, by a blade, completely through crease rolls, to form the final main fold in the finished booklet. The finished booklets are then accumulated in a tray downstream of the crease rolls.
A practical problem with booklet makers having crease rolls relates to the fact that, when a set of sheets to be folded into a booklet enters the nip formed by the crease rolls, there is a sudden change in frictional coefficient between the crease rolls, especially between the outermost sheet in the folded set (such as forming the cover of the booklet) and the neighboring sheet in the set. The change in torque between the crease rolls can result in damage to the outer sheet of the set.